A series of compounds will be synthesized for the purpose of developing agents that may have future use as orally active antihypertensive drugs. These compounds will be nonpeptides modeled after known peptide inhibitors of angiotensin-converting enzyme. A select number of nonpeptide analogs containing no amide bonds will be synthesized initially. These compounds will be tested in an angiotensin-converting enzyme in vitro assay for inhibitory activity. If reasonable inhibitory activity is found, more structurally related nonpeptide analogs of this type will be synthesized and tested. If these first nonpeptide analogs have no inhibitory activity, nonpeptide analogs containing an appropriately positioned amide bond will be prepared. The amide bond found in these compounds will be altered, compared with that found in the corresponding peptide inhibitors, in ways that would be expected to stabilize the amide linkage to peptidase cleavage. These compounds also will be tested in the same in vitro enzyme assay for inhibitory activity. All compounds showing good activity in the in vitro assay will be tested further in the hypertensive rat. The compounds will be tested first for antihypertensive activity when given intravenously. Those compounds that show intravenous activity will be tested for oral activity in rats.